1. Field of the Invention
The present invention generally relates to a method, system and apparatus for image forming and processing, and more particularly relates to a method, system and apparatus for image forming and processing that is capable of adjusting input and output properties in an appropriate manner.
2. Discussion of the Background
In general, image forming systems such as digital copying machines, for example, having input and output stations as well as an image processing station have been provided in a variety of forms. For example, an input station which reads an original image and converts a read image into digital data can be separated as a form of a scanner, for example. Also, an output station which outputs on a recording sheet can be separated as a form of a printer, for example. An image processing station can also be a single apparatus such as a personal computer. These separated units can be put partly or totally in one apparatus or operatively be connected using a network such as a local area network, for example.
However, any one of these variations of the image forming system cannot be successful to neglect a basic rule in that a quality of an image is determined by the input and output properties inherent to the input and output stations, respectively. In particular, an image forming system built up in a network environment may provide users with a variety of combinations of personal computers, scanners, and printers. Using a different combination generally results in a different image quality, mostly bad quality.
Japanese Laid-Open Patent Publication No. 9-172543 (1997) describes an image forming system which adjusts property information in response to image forming processes and output modes and performs an image processing operation using the adjusted property information to obtain an output image in an optimal quality. In another image forming system, image data is separated into a plurality of image areas according to a type of an image area and each image area is handled with an image processing operation so as to obtain an output image in an optimal quality.
However, the above-mentioned systems merely correct for spatial frequency properties of a specific scanner and a specific printer. Therefore, the above-mentioned way is not sufficient to generate a precision image output when using a scanner and a printer randomly selected.
Also, input properties such as a resolution property, an MFT (modulation transfer function), and the like inherent to an image input apparatus are very important factors for the image area separation operation, and a simple uniform application of the image area separation operation relative to the whole range of these input properties may result rather in a bad image quality. For example, if an image area separation technique having algorithms optimized at a resolution of 400 dpi is used relative to image data having a different resolution, a result of the operation will mostly be inferior in comparison with the original image.
For example, an image with a degraded MTF shows, in particular, a smoothed edge at which a simple uniform application of a technique for finding an edge specific pixel cannot properly be operated. Commonly, in such a case, a pretreatment is executed, that is, an MTF correction filter is used to enhance the MTF. But, the MTF correction filter may also enhance electrical noises included in the image signal when the MTF is degraded to an extreme extent. This causes an event in which a character image area is erroneously mixed in a pattern image area or in which a pattern image area is erroneously mixed in a character image area. As a result, an output image will be inferior in comparison with the original image.
As described above, the image area separation operation relies largely on the resolution property and the MTF property of the scanner. Therefore, the image area separator operation adjusted to a specific resolution and a specific MTF cannot properly handle an image having a resolution and an MTF which are greatly different from the specific resolution and the specific MTF of the image area separation operation. For example, a high resolution scanner can generally increase a detection accuracy in an edge image detection for detecting an edge portion of an image or a screened-print image detection for detecting an image made with a screen, by increasing a size of a matrix used in a pattern matching test. But, if it is not possible to use a large size matrix due to any reason such as a limitation from a host apparatus, such a high resolution scanner cannot perform the image area separation operation at a preferred performance. This results in an inferior image in which a pattern image area may include several points wrongly judged as character image areas and a character image area may include several points wrongly judged as pattern image areas.
There would be at least two efficient ways to handle such an image, having an image at which it is difficult to properly perform the image area separation operation, so as to generate a superior output image. A first way is as follows. An object image is first determined whether it is a pattern image or a character image by examining the data of the object image and is then subjected to an image processing operation entirely under a pattern image mode or a character image mode in accordance with a result of the determination. In this case, the image area separation is not performed. A second way is to perform the image area separation only at an area where it is assured that the image area separation can properly be performed and to handle other areas under the pattern image mode or a character image mode.
Minimizing an application of the image area separation operation as described above will also provide a benefit in reduction of a process time to a software-implemented image area separation operation.
Furthermore, a recent trend in the computer industry shows the explosion in the use of a digital still camera and a digital video camera and, in such a time, input images are more pictures of landscapes and people by far than characters. Therefore, the image forming system which handles the input images entered through these cameras needs to perform the image processing operation more suitable to the picture image.
As for a filtering process, a filter enhancing a high frequency band will be selected for an image having an extremely low frequency property in a high frequency band so as to come close to a target property when an input property of an image input apparatus is randomly combined with an output property of an image output apparatus. In this case, an output image from an original image such as a picture or a painting may have an aliasing, a noise from an isolated point, or the like and be therefore inferior.